Author: Jesse Khalil

New feature in OPUS Projects: Using RTN vectors to support 2022 Transformation tool

February’s column focused on potential errors in orthometric heights using a digital barcode leveling system with multi-piece leveling rods. As stated in the column, businesses need to make decisions based on expenses and ultimately on the profit margin; but making a business decision that results in a bad technical outcome is never the right decision. This newsletter column is going to highlight a new feature in the National Geodetic Survey (NGS) Beta OPUS Projects 5.1 routine permitting the use of RTN vectors to support the development of the 2022 Transformation model.

On Jan. 12, NGS held a webinar titled “Using RTN Data in OPUS Projects 5 for GPSonBM.” Users can download the video and PowerPoint slides here.

I’ve been highlighting NGS’s GPS on Bench Mark program that supports the 2022 Transformation Tool in my columns since 2018. NGS delayed the completion date for the new modernized NSRS until 2025, so they have extended the cut-off date for submitting GPS on Bench Mark data for use in the 2022 Transformation Tool until Sept. 30.

NGS GPS on BenchMarks Program (Image: NGS website)

NGS has been developing tools that facilitate submitting data to the NGS GPS on BM campaign such as OPUS Share. The latest tool is the OPUS Project 5.1 routine that allows the use of RTN vectors. OPUS Projects 5.1 is a beta product, but NGS is now allowing users to use the routine to submit data for the GPS on BM campaign. My October 2021 column highlighted NGS’s Beta OPUS Projects 5.1.

The 2023 requirements for using OPUS Projects in the GPS on BM program (Image: NGS website)

I’d like to note that OPUS has been updated to support the newly released ITRF2020 (IGS20) orbits. My October 2022column discussed the latest International Terrestrial Reference Frame of 2020 (ITRF2020) released by the International Earth Rotation and Reference System Service (IERS). A previous NGS news bulletin provided a statement about the new reference system and products.

Excerpt from NGS News Bulletin (Image: NGS website)

Clicking on the link titled “NEW: 2023 Requirements for Use in the GPSonBM Campaign” on the OPUS Projects 5.1 webpage provides the requirements for using OPUS Projects 5.1 and Real-Time Network (RTN) data to support the 2022 Transformation Tool; that is the 2023 GPS on BM campaign. There are five sections in the writeup: Introduction, Project Planning, Equipment and Configuration, Field Requirements and Office Requirements. The Introduction section states that the requirements are limited to the GPS on BM Campaign and will be replaced, or superseded, when NGS finishes its new GNSS surveying specifications.

Introduction Section from Requirement Write Up (Image: NGS website)

The project planning section of the announcement states that RTN vectors of 5-minute occupations can be used instead of the 4-hour occupations required for OPUS Share.

Project Planning Section from Requirement Write Up (Image: NGS website)

However, the Field Requirement section states that the mark must be occupied three different times.

“During the RTN survey, measure each mark in your project (including the RTN Validation Station) for a minimum of 5 minutes for three independent occupations. All three measurements must agree by 3 cm horizontal and 5 cm ellipsoid height. They also must be separated by at least 3 hours (even if occupied on different days). Plan to occupy a mark, go occupy a few more in the area, then circle back. Or rotate day-by-day,” the section states.

Field requirements Section from Requirement Write Up (Image: NGS website)

As stated in the section on office requirements for using OPUS-Projects 5 in the 2023 GPS on BM Campaign writeup,“The OPUS-Projects User Guide provides instructions on how to run the software and submit a project to NGS. The User Guide states to follow the steps in the order listed below, and it explains steps 1 – 7 and 9 – 11 in detail. For step 8 and when including GVX data in OPUS-Projects 5, refer to those portions of the User Guide’s Quick Start which are highlighted in yellow. NGS is working on fully updating the User Guide to include more details; for now, use the Quick Start Guide for assistance with GVX.”

OPUS Projects User Guide (Image: NGS website)

Quick start guide. (Image: NGS website)

I recently used OPUS Projects to analyze some GNSS results using Harris-Galveston Subsidence District CORS and PAMS GNSS data. I want to emphasize that it may seem like a lot of work the first time you use the routine, but NGS makes it fairly simple to complete each task. The manual is very complete and does a good job of describing every step. The manual can be downloaded here. In my experience, the most time-consuming task is creating the descriptions. There are several items that must be correctly entered because the answer to some entries affect the answers to other entries. That said, NGS supports a description entry software called WinDesc that facilitates entering the appropriate information. The OPUS Projects User Guide provides an appendix that describes using the WinDesc module to enter description metadata.

For marks that are in the NGS database, known as the NGS Integrated Data Base (NGSIDB), WinDesc will import information from NGSIDB, thereby decreasing the number of entries users need to address. In other words, if the mark has a PID then it should be in the NGSIDB. If you are occupying a mark that is part of NGS GPS on Bench Marks website then it probably has a PID and a description in NGSIDB.

Example of PID from Mark Priority List (Image: NGS website)

I’ve included three slides from the Jan. 12 webinar that summarize the basic requirements.

This slide is a depiction of how a CORS station must be connected to the RTN vectors. (Image: NGS website)

This slide provides the occupation and precision requirements. (Image: NGS website)

This slide provides a list of the required metadata for the project. (Image: NGS website)

As for the requirement of at least three independent RTN occupations on different times, in my opinion at least one occupation should be on a different day. My October 2021 column addressed a study that reported on using RTN solutions to estimate accurate horizontal and vertical coordinates.

The report stated, “When differenced with coordinates from a static GNSS survey campaign, the horizontal and vertical RMSE of the NRTK-derived coordinates was 2.3 cm horizontally and 4.5 cm vertically at 95% confidence. Repetitive NRTK vectors on each baseline differed between ± 2.4 cm horizontally and ± 3.4 cm vertically at 95% confidence.”

The report also stated, “Adjustment of hybrid survey networks with four repeat NRTK vectors per bench mark produced network accuracies at 95% confidence for the adjusted coordinates at all bench marks less than 1 cm horizontally and 2 cm vertically (ellipsoid height).”

The requirements are limited to the GPS on BM Campaign and will be replaced, or superseded, when NGS finishes its new GNSS surveying specifications.

(Image: Screenshot of Accuracy of GNSS Observation from Tree Real-Time Networks in Maryland, USA)

The paper by Gillins, et. al was presented at the 2019 FIG Working Week held in Hanoi, Vietnam, on April 22–26, 2019. The International Federation of Surveyors (FIG), involves a wide range of professional fields within the international surveying community; this includes surveying, cadastre, valuation, mapping, geodesy, hydrography, and geospatial and provides an international forum for discussion and development to promote professional practice and standards. FIG meetings are held all over the world. I’d like to highlight that the 2023 FIG Working Week is going to be held in Orlando, Florida, on May 28 – June 1, 2023.

NGS will be presenting a full-day worth of content on NSRS Modernization during the FIG Working Week 2023. For the first time in more than 20 years, this annual FIG gathering will take place in the United States, hosted by the National Society of Professional Surveyors (NSPS).

I’ve participated in several FIG meetings. I’ve learned a lot from presentations as well as holding hallway meetings with experts from the international surveying and mapping community. All geospatial users should plan on attending this event. I have provided information about the FIG commissions in my August 2021 newsletter. I would encourage everyone to visit the FIG website and review the information about the 2023 FIG Working Week. The a list of the FIG Commissions can be found here. More information can be obtained on each commission by clicking on its title.

Future columns will highlight the FIG Working Week as the agenda is developed. I would encourage everyone to check NGS’s Website for updates on Beta products and new surveying specifications. Geospatial users should also subscribe to NGS’s News Services at the following here. Check out the NGS News Services site for what’s available.

March 1, 2023
ICA Summit 2023 registration now open

The third Innovative, Connectivity, Autonomous (ICA) Summit will take place May 15-16, 2023, in Frankfurt, Germany.

The ICA Summit 2023 will focus on the various levels of automated vehicles and how the industry is being redefined by fast-changing technology. Industry professionals will discuss how manufacturers and suppliers will integrate key connectivity requirements to achieve advanced levels of autonomous driving.

The closed-door ICA Summit will dive into innovative solutions and regulatory framework of development and validation. Attendees will have a chance to explore the latest developments in the industry and share their insights on the following topics:

• “Autonomous vehicles: Future is today”
• “Connectivity should not be an option for today’s vehicle”
• “ADAS: From ABS to level 5”
• “Software and hardware: The key to superior AI”

For more information and to register, visit the ICA Summit 2023 website.

February 27, 2023
IPIN 2023 paper submissions now open

Fraunhofer IIS has opened paper submissions for The International Conference on Indoor Positioning and Indoor Navigation (IPIN) 2023, which takes place Sept. 25 -28 at the Nordostpark in Nuremberg, Germany.

The event is dedicated to indoor positioning, its applications and recent developments. The last decade has seen tremendous technical advances in indoor positioning. However, unlike the GNSS solutions established in the outdoor environment, there is not yet a technology that is affordable and accurate enough for the general market.

The potential applications of indoor localization are all-encompassing, from the home to vast public areas, from internet of things and personal devices, to monitoring applications.

The conference expects to attract up to 300 industrial and academic experts from the fields of computer science, electronics and surveying to address these challenges and the future of the industry.

To learn more about the conference and paper submissions, visit INIP-Confrence.org.

February 15, 2023
Industry Day: Find out how to take part in low-orbit satnav testing

The European Space Agency (ESA) is in search of European companies interested in taking part in the in-orbit demonstration of a low-Earth-orbit (LEO) satellite navigation constellation utilizing novel frequencies and capabilities.

Those interested in participating are encouraged to attend ESA’s LEO-PNT Industry Day on March 7 at the ESTEC technical center in the Netherlands. The LEO-PNT Industry Day will give an overview of the project to companies, research institutions and ESA delegates from Member States.

A detailed invitation will be issued soon, covering all aspects of the LEO-PNT Orbit Demonstrator, including the space and ground segments, operations, launchers, the test user segment, experimentation, and segment demonstration.

Registration by Feb. 27 is required. To learn more, visit atpi.eventsair.com.

LEO satellites would supplement the existing Galileo constellation. (Image: ESA)

February 14, 2023
How to select an INS for mobile mapping

Image: OxTS

OxTS has shared this piece on OxTS.com.

Mobile mapping is helping accelerate the progression of some of the most difficult engineering challenges on the planet, including those around autonomous driving and advanced surveying techniques, such as lidar.

The complexity of those challenges means that the outputs from a mobile mapping inertial navigation system (INS) must be as accurate as possible. A high-performing INS will make the most of any available GNSS signals, with the aim of providing centimeter-level accuracy even in areas where GNSS performs poorly, for instance in urban canyons. It also offers important data on pitch, roll and heading, which maintains the integrity of survey data even as the vehicle moves across large areas.

With such a wide variety of INS devices on the market, it can be difficult to narrow down the best option. It is important to establish criteria that will aid in evaluating the different INS propositions out there for mobile mapping projects.

Image: OxTS

1) How tightly integrated are the inertial measurement unit (IMU) and GNSS data?

INS is an essential element in providing accurate location data in as many environments as possible. Therefore, it is important to know how effectively the data from the IMU supports the GNSS data. In technical terms, this means evaluating whether the sensors are tightly integrated at all, and if so, how well.

The reason GNSS struggles in urban canyons and under tree canopies is that it is unable to get the six satellite signals necessary for a real-time kinematic (RTK) lock. In this situation, the GNSS will give readings that may be incorrect, as it is essentially trying to solve an equation without having all the numbers.

A tightly integrated GNSS and INS data stream will select the most reliable signals and use those to determine the position of the vehicle. If the data streams are not tightly integrated, then the INS’ ability to counteract GNSS issues is limited. Without accurate positioning, data scans will lose accuracy and even become completely incoherent the longer the user scans — making them unreliable at best, and unusable at worst.

2) Trading off accuracy and cost

Although accuracy is vital in mobile mapping, some INS devices will provide data that is far more accurate than the given job requires. Because greater accuracy equals greater cost, users may be paying more than necessary.

With that being said, the scale of accuracy and cost is not linear. An INS half the price of the most expensive one on the market will not be half as accurate. Look at each offering carefully to see what it includes and decide what level of accuracy and features are vital to the task. Eliminating unnecessary levels of precision or additional software features that are not needed is an effective way to make some savings.

3) How rugged is the device?

Mobile mapping vehicles will likely be out in the dry, wet, hot, cold, mud and snow. These vehicles will almost certainly be used consistently for long periods of time. Thus, it is essential to know that none of these conditions will stop the INS from working at peak effectiveness. Look for the IP rating (IP65 is essential for being weatherproof and protecting against shocks and dust) and ask what the average lifespan of the product is.

Image: OxTS

4) Can the device be properly calibrated?

Any INS is only as good as its calibration. Without calibration, the sensors in any INS can become misaligned and therefore provide inaccurate readings. Talk to vendors about their calibration processes — do they work to a nationally recognized standard of calibration like ISO 17025? Do their calibrations account for variations in temperature or humidity?

It is also worth considering how often sensors need recalibration. Recalibration is a chargeable service from most vendors, meaning the more the device needs recalibrating, the more the user will have to pay. This could also lead to delays if the user must send units abroad to have them recalibrated.

February 9, 2023
Certus Evo helps Nextcore’s UAV Lidar Fly To New Heights

Advanced Navigation’s Certus Evo enabled Nextcore to fly at 100 metres AGL, exceeding their goal. Nextcore required a MEMS INS that would enable their UAV-LiDAR to fly at 80 metres above ground level (AGL).

Discover Certus Evo.

This video is sponsored content by Advanced Navigation.

February 9, 2023
One GPS Mystery Solved, Another Remains

Ever since it came on-line in February 2022, the website GPSJam.org has shown what appears to be regular interference with GPS signals in Texas near San Antonio and Del Rio, and locations north and south of Oklahoma City, Oklahoma.

Only on normal workdays, however. Not on weekends or holidays. Furthermore, whatever was happening also took time off between the Christmas and New Year holidays GPSJam.org also shows similar, though less regular, activity in New Mexico. Experts say this is easily explained as White Sands Missile Range is often the site of electronic warfare training and tests. These are always announced in advance in FAA Notices to Air Missions (NOTAMs) when any interference with GPS reception is anticipated.

The regular patterns observed in Texas and Oklahoma and the lack of NOTAMs led some experts to speculate the source could be inadvertent interference from a commercial or government activity. Said one former official, “It’s just the kind of pattern you see from large organizations. They are off every weekend, federal holidays, and around Christmas.”

Aerobatic-capable Military Training aircraft reporting low NIC values (Image: Stanford University)

GPSJam.org is the brainchild of aviation analyst John Wiseman. The site uses crowdsourced ADS-B reports gathered by the ADS-B Exchange and displays it on a world map. Areas in yellow indicate that between two and ten percent of ADS-B reports for the day had low navigation accuracy. Areas in red had ten percent or more.

Information from the site has proved useful in identifying patterns of regular GPS jamming and spoofing in Russia and other conflict areas around the globe.
The workday patterns in Texas and Oklahoma have appeared on GPSJam.org displays since the site went live in February 2022.

GPS Interference and Aviation

Minor interference with GPS signals is fairly common. GPS jamming devices, while illegal to use, are inexpensive and easy to obtain from vendors on the internet.

Truck drivers wanting to defeat their company’s fleet tracking system, people concerned about being tracked by the government or others, even ministers trying to keep parishioners from texting during sermons – all have been known to use such devices.

Most GPS interference is unintentional. A two-year European Union study found hundreds of thousands of potentially harmful signals, but judged only about ten percent to be intentional. The rest were the inadvertent byproduct of poorly tuned electrical and electronic equipment.

ADS-B tracks of training aircraft performing aerobatics. Red indicates low NIC value reported. (Image: Stanford University)

While most GPS interference is unintentional and localized, spurious signals powerful enough to noticeably impact airborne operations are not unknown.

In two separate incidents last year strong interference near the Denver and Dallas airports impacted air traffic, each for more than a day. The Denver incident lasted for 33 hours before authorities found the source and shut it down. Air traffic was disrupted at Dallas for 44 hours according to government sources, though researchers found the actual interference only lasted for 24 hours. The source of the disruption was never identified.

In 2019 a passenger aircraft was almost lost due to GPS interference while on approach to Sun Valley, Idaho’s Friedman Memorial Airport. As the aircraft flew a GPS-based approach in smoke and haze, the interfering signal was just strong enough to lure it off course and toward a mountain. Fortunately, a sharp-eyed radar controller hundreds of miles away spotted the problem and intervened in time. The source of the interference was never identified.

As a result of the Sun Valley incident and input from numerous aviation groups, the International Civil Aviation Organization told its members there was an “urgent need to address harmful interferences” to satnav signals.

Texas and Oklahoma Mystery Solved

A researcher at Stanford University finally solved the puzzle of the strange recurring sequence of reports from Texas and Oklahoma.

While investigating last October’s GPS interference event near the Dallas airport, PhD candidate Zixi Liu noticed aircraft outside the main area of effect also reporting low Navigation Integrity Category (NIC) values. This began before and continued after complaints from commercial airlines about GPS not being available at Dallas-Fort Worth. These aircraft were in the same general area of Texas, but far enough away that there were large areas between them and Dallas that did not contain any reports with low NIC values.

Low navigation accuracy reports displayed at GPSJam.org. in New Mexico reports were due to GPS interference from military testing. In Texas and Oklahoma, military aerobatics training likely caused reports of low navigation accuracy. (Image: GPSJam.org)

At the same time MS Liu was also investigating anomalous ADS-B reports near San Antonio and Del Rio, Texas. She discovered in all three cases the reports of low NIC values were coming from military training aircraft regularly used for aerobatics. Other aircraft nearby reported good NIC values and showed no evidence interference.

In a recent presentation to the Institute of Navigation, she postulated that Interference with GPS signals was not the cause of the low navigation integrity reports. Rather, the rapid maneuvers and unusual aircraft attitudes of aerobatics caused the airplanes’ navigation receivers to intermittently lose lock on signals from GPS satellites. This caused their ADS-B equipment to report low navigation integrity.

Having solved that mystery, Ms. Liu continues to work on her original question – identifying the source of October’s 24-hour GPS disruption near the Dallas-Fort Worth airport.

Mr. Dana A. Goward is the President of the Resilient Navigation and Timing Foundation and a former US Coast Guard helicopter pilot.

February 7, 2023
OGC announces Geo for Metaverse Domain Working Group

Image: OCG

The Open Geospatial Consortium (OGC) has formed the Geo for Metaverse Domain Working Group (DWG), which will serve as a forum for the collective geospatial expertise of the OGC community to gather to help build and expand the open Metaverse. The group is open to both OGC members and non-members.

The group plans to contribute its expertise in 3D, modeling and simulation, artificial intelligence, digital twins, streaming, augmented and virtual realities, routing, mapping and more — all at scale.

The group will work on pieces of the Metaverse that pertain to geospatial applications and standards by identifying standardization activities and best practices based on FAIR (making data Findable, Accessible, Interoperable and Reusable) data principles.

The DWG will be the primary point of contact with the Metaverse Standards Forum, of which OGC is a founding and principal member.

3D geospatially anchored data is powering innovation across a range of industries. This same data — relied upon for construction of the real world — is now driving the creation of virtual/digital worlds that will form parts of the Metaverse.

Learn more about the mission, goals and planned activities of the group on the OGC Geo for Metaverse DWG homepage.

February 1, 2023
JNC 2023 abstract deadline is fast approaching

Photo: ION

Abstracts for Joint Navigation Conference (JNC) 2023, “Enhancing Dominance and Resilience for Warfighting and Homeland Security PNT,” are due Feb. 3. JNC 2023 is the largest United States military positioning, navigation and timing (PNT) conference of the year with joint service and government participation.

The Institute of Navigation’s Military Division will host the conference June 12-15 at the Town and Country Hotel in San Diego. The event will be open to all conference participants, exhibitors, their employees and related organizations. All materials displayed in the exhibit hall will be publicly released after review.

The event will focus on advances in PNT with an emphasis on joint development, testing and support of affordable PNT systems, logistics and integration. Additionally, the conference will cover advances in battlefield applications of GPS, critical strengths and weaknesses of field navigation devices, warfighter PNT requirements and solutions and navigation warfare.

Abstracts must be written for public release with the intent to present in a Controlled Unclassified Information (CUI) U.S. only environment. Abstracts not approved for public release will not be accepted.

Interested parties may submit their abstracts at ion.org/jnc.

January 12, 2023